Buckle fastener



FIG. 1 is a perspective view of a buckle fastener showing my new design, the broken line showing of a strap and second buckle is for illustrative purposes only and forms no part of the claimed design;

FIG. 2 is a front elevational view;

FIG. 3 is a bottom plan view;

FIG. 4 is a rear elevational view;

FIG. 5 is a right side elevational view;

FIG. 6 is a left side elevational view; and

FIG. 7 is a top plan view. 

The ornamental design for a buckle fastener, as shown and described. 